How do I extrude an imported svg along the z axis without clipping the original shapes?
This sort of thing can happen when your object has a very extreme scale.

To fix it, apply the scale with &#9096; CtrlA> Apply Scale.



When you scale an object in object mode the mesh data is not changed, but it will be distorted according to the scale in a non-destructive way (like a modifier). Since your object was scaled up by such a huge amount, it caused some distortion; probably due to precision error.